1. Field of the Invention
The present invention relates to semiconductor devices and, more particularly, to a semiconductor device suitable for a camera module which integrally packages a light-receiving element and an image-pickup lens.
2. Description of the Related Art
In recent years, portable telephones and portable personal computers equipped with a small camera have been developed. For example, a portable telephone equipped with a small camera picks up an image of a calling person by the small camera so as to acquire image data and sends the image data to a person on the line. Generally, such a small camera is constituted by a CMOS sensor and a lens.
Miniaturization of portable telephones and portable personal computers has been progressed further, and there is also a demand for miniaturization of small cameras used for these equipments. In order to satisfy the demand for miniaturization of such a small camera, a camera module which integrates a lens and a CMOS sensor has been developed.
The above-mentioned camera module is formed as a small module by incorporating an image-pickup lens, an imaging device and a semiconductor element into a mold resin. The camera module has the same structure as a semiconductor device which has a semiconductor element encapsulated in a mold resin, and is connectable to a circuit board by using bump-chip-carrier (BCC) electrodes as external connection terminals. As an example of a BCC electrode, there is an electrode formed of a protrusion made of a mold resin and covered with a metal film on an outer surface of the protrusion. Such a BCC electrode is generally referred to as a resin bump.
FIG. 1 is a cross-sectional view showing an example of a semiconductor device having a resin bump. FIG. 2 is a cross-sectional view showing another example of the semiconductor device having a resin bump.
The semiconductor device shown in FIG. 1 has a semiconductor element 1 encapsulated by a mold resin 2. A metal film 3 is formed on the bottom (mounting side) of the mold resin 2. The metal film 3 is patternized so as to form circuit patterns. The semiconductor element 1 is arranged within a mold resin 2 in a face-up state where a circuit formation surface faces upward, and an element-fixing resin 4 is provided on the backside of the semiconductor element 1. The element-fixing resin 4 is an adhesive used for fixing the semiconductor element 1 onto the circuit board in the manufacturing process. Electrodes of the semiconductor element 1 are connected to the metal film 3 (pattern wiring) by bonding wires 5.
The resin bump 6 is formed on the bottom (mounting side) of resin mold 2. The resin bump 6 is formed by forming a protruding part made of the mold resin and forming the metal film 3 on the protruding part. The metal film 3 positioned at the end of the protruding part serves as an external connection electrode. Such a resin bump can be formed by forming on a base board a recess corresponding to the protruding part, forming a resin bump using the recess and thereafter removing the base board.
FIG. 2 shows the semiconductor device shown in FIG. 1 in which the semiconductor element 1 is arranged in a face-down state where the circuit formation surface faces downward. Protruding electrodes are formed on the semiconductor element 1, and the protruding electrodes are connected to the circuit patterns formed by the metal film 3. The circuit formation surface of the semiconductor element 1 is filled up with an under-fill material 7. The resin bumps 6 are formed on the bottom (mounting side) of the mold resin 2 similar to the semiconductor device shown in FIG. 1.
The structure of the semiconductor device having resin bumps as shown in FIGS. 1 and 2 is preferably used for producing a small camera module.
As a structure of the camera module which can be miniaturized, there is suggested a camera module in which a resin mold provided with a through opening for receiving light and wiring pattern is connected to a circuit board having a through hole, an imaging device being flip-chip mounted on one surface of the resin mold and a lens holder for image formation is mounted on the other surface in a state where the lens holder covers a space above a light-receiving part. The imaging device detects a light at the light-receiving part or a device surface on which a micro lens is present and apply a photoelectric transformation to the detected light, and provides the thus-obtained image signal to a signal processing circuit, etc. so as to display a picture on a screen of a display device or the like.
FIG. 3 is a cross-sectional view of a camera module using the structure of the semiconductor device shown in FIG. 1. FIG. 4 is a cross-sectional view of a camera module using the structure of the semiconductor device shown in FIG. 2.
The camera module shown in FIG. 3 has an image-pickup lens 11 attached to a lens holder 10. The lens holder 10 is mounted on the upper surface of a molded body 12 (corresponding to the mold resin 2 of FIG. 1), and an imaging device 13 is attached to the undersurface of the molded body 12. Provided inside the molded body 12 is a semiconductor element 14 (corresponding to the semiconductor element 1 of FIG. 1). Electrodes of the semiconductor element 14 are connected to the pattern wiring which consists of a metal film 15 formed on the bottom (mounting side) of the molded body 12 by the bonding wires.
Resin bumps 16 are formed on the bottom of the molded body 12, and are electrically connected to the electrodes of the semiconductor element 14 and the imaging device element 13 through the pattern wiring which consists of the metal film 15. Additionally, the resin bumps 16 are connected to the pattern wiring 18 of the wiring board 17. The wiring board 17 is a flexible board, and is provided with a pattern wiring made of a copper foil or the like on a polyimide substrate 19. The camera module is connected to an external circuit through the wiring board 17.
In the camera module of the above-mentioned structure, a light passed through the lens 10 passes a filter glass 20 and is incident on the imaging surface of the imaging device 13. Thereby, an electric signal corresponding to the image on the imaging surface is output from the imaging device 13. The semiconductor element 14 applies image processing to the electric signal from the imaging device 13, and outputs the processed signal to the wiring board 17 through the resin bumps 16. Thus, the imaging device 13 and the semiconductor element 14 are efficiently connected to the wiring board 17 by the resin bumps 16 formed using the resin of the molded body 12.
FIG. 4 shows a structure in which the semiconductor element 14 is arranged in a face-down state where the circuit formation surface faces downward in the camera module shown in FIG. 3. Projection electrodes are formed on the semiconductor element 14 and are joined to the circuit pattern formed by the metal film 15.
It should be noted that Japanese Laid-Open Patent Application No. 9-162348 may provide a background of the present invention.
The semiconductor devices shown in FIGS. 1 and 2 have the structures in which the resin bumps 6 are arranged around the semiconductor element 1. Thus, if the semiconductor element becomes large and a number of electrodes is increased, there is a problem in that the size of the semiconductor device itself becomes large.
The above-mentioned problem also occurs in the camera modules shown in FIGS. 3 and 4. That is, when the semiconductor element 14 (for example, a processing element) is mounted in addition to the imaging device 13, it is preferable, in order to attempt miniaturization of the module, to take a structure in which the semiconductor element 14 is embedded in the encapsulation resin that forms the molded body 12 unlike the externally attached imaging device. However, it is a subject to miniaturize a module while using the resin bump since the module size becomes inevitably large when forming the resin bumps with the encapsulation resin.